DE102013222839A1 - Method for operating a camshaft adjuster - Google Patents

Abstract

A method for operating a camshaft adjuster of an internal combustion engine provides that in a start-up phase of the camshaft adjuster, the camshaft is adjusted in a first adjustment direction which is dependent on the operating data of the camshaft adjuster and / or the internal combustion engine available at the time (T0) of the start-up, and that a target value (ZP) of the phase angle φ of the camshaft is set in a setting phase following the start-up phase. The transition between the start-up phase and the setting phase can take place before an end stop of the camshaft adjuster is reached.

Description

Field of the invention

The invention relates to a method for operating a camshaft adjuster of an internal combustion engine, in particular an electric camshaft adjuster, wherein the starting of the camshaft adjuster is covered by the method.

Background of the invention

From the DE 10 2008 039 008 A1 For example, an electromechanical phaser is known that utilizes a three-shaft transmission that includes an actuator shaft, a camshaft sprocket, and a camshaft. A drive of the control shaft already takes place during the engine standstill or in a transition phase in which at least one of the three shafts of the three-shaft transmission is stationary. It is envisaged to pre-position the camshaft regulated or unregulated, whereby in the latter case a "blind" adjustment takes place in one direction. In contrast, there is a continuous target-actual comparison with controlled adjustment, the DE 10 2008 039 008 A1 does not elaborate on the regulation.

Another camshaft adjuster with electric actuator is for example from the WO 2004/027223 A1 known. In this camshaft position sensor position sensors are provided both on the crankshaft, on the camshaft, as well as on the adjusting device itself. A targeted phase adjustment of the camshaft is thus possible even at low speed or at standstill of the internal combustion engine. Before the camshaft adjuster is operated in a regulated manner, it can first be brought into a defined position immediately after the start by approaching a reference mark, which may be an end stop of the camshaft adjuster.

Object of the invention

The invention has for its object to further develop the starting behavior of a camshaft adjuster, in particular with electric actuator, compared to the cited prior art.

Description of the invention

This object is achieved by a method for operating a camshaft adjuster of an internal combustion engine according to claim 1 and by a method for operating a camshaft adjuster of an internal combustion engine according to claim 2. With one and the same camshaft adjuster is in various embodiments of the invention either only the method of claim 1 or only the method according to claim 2 or both the method according to claim 1 and the method according to claim 2 realized. Further, the object is achieved by a control unit, which is designed in an internal combustion engine for operating a camshaft adjuster according to claim 1 and / or claim 2.

The operating method according to the invention comprises the start-up phase of the camshaft adjuster and a subsequent adjustment phase in which a target angle of the camshaft is adjusted and thus the regular, permanent operation of the camshaft adjuster is achieved. During the start-up phase, the camshaft is adjusted in a direction that may differ from the direction of adjustment in the subsequent adjustment phase.

In the method according to claim 1 takes place in the transition from the startup phase to the adjustment phase, a reversal of the adjustment, said reversal is triggered by detecting an angular relation between the camshaft and crankshaft of the internal combustion engine before reaching an end stop of the camshaft adjuster. In the simplest case, a blind adjustment of the camshaft takes place in the start-up phase. It only becomes apparent in the course of the adjustment process whether the correct target angle of the camshaft is actually approached with this adjustment. If this is the case, the adjustment is maintained in the adjustment phase.

If this is not the case, however, a change of direction in the sense of claim 1 takes place with the transition from the startup to the adjustment phase. In a vehicle which is driven by an internal combustion engine with a camshaft adjuster, the method according to claim 1 is only applied to a part of Starting operations performed. Even with the starting operations, for example, statistically in about half of the starting operations, in which a reversal of the adjustment of the camshaft adjuster takes place, the method of claim 1 is not necessarily carried out every time. Instead, for example, in a part of the starting operations, which include a change in direction of the camshaft adjustment, the first, during the start-up phase running adjustment until reaching a stop position of the camshaft adjuster persist. Such an adjustment up to an end stop is considered, for example, to specifically approach a particular well-defined setting of the camshaft adjuster during individual starting operations and thus to test or set measuring devices. Otherwise, an adjustment of the camshaft adjuster is up to an end stop, the achievement of which triggers the transition from the start-up to the adjustment phase, in particular conceivable when the end stop is reached, before an existing measuring system has detected the angular relationship between the camshaft and crankshaft of the internal combustion engine.

In the method according to claim 2, which can be combined with the method according to claim 1, the initial adjustment direction of the camshaft, that is, the adjustment in the startup phase of measured or otherwise determined operating data of the camshaft adjuster and / or other components of the internal combustion engine dependent. The operating data of the internal combustion engine including the camshaft adjuster can relate to a wide variety of parameters of the internal combustion engine or environmental parameters, as long as there is a physical relationship between the respective parameter and the operation of the camshaft adjuster.

Operating data, on which the initial adjustment direction of the camshaft depends, can in particular be boundary conditions such as air pressure or operating temperatures, for example an oil temperature. The target angle of the camshaft can also be included in the determination of the initial adjustment direction, whereby the target angle alone is by no means the only criterion for determining the adjustment direction in the startup phase. For example, it can be checked as part of the definition of the startup strategy of the camshaft adjuster to what extent existing electrical loads in the vehicle in addition to the camshaft adjuster need electrical power. If a high power consumption of other consumers is given, then, for example, in the startup phase of the camshaft adjuster initially gentle in terms of power supply adjustment of the intake camshaft direction "early" to at a later date, namely the transition to the adjustment phase, the adjustment direction "late " switch.

In order to limit the power consumption during the start-up phase of the camshaft adjuster, the adjustment speed during this phase may be limited to a value below the maximum adjustment speed. In particular, operating modes of the internal combustion engine can be realized in which initially no adjustment of the camshaft takes place when the internal combustion engine is started. In other modes of operation, which are selected automatically, for example, as long as no limitation of the power supply of the camshaft adjuster - for example, by a nearly discharged traction battery - can be expected, however, the camshaft can be adjusted shortly before starting the engine. During the start-up phase of the camshaft adjuster can realize in process variants, the features of claim 1 and / or claim 2, in addition to a temporary stoppage of the adjustment also a single or multiple change of adjustment, such as for the purpose of breakaway of the camshaft adjuster, especially after longer periods and / or at very low temperatures.

A variant of the method comprising both the features of claim 1 and the features of claim 2 may be designed, for example, as follows:
First, based on a plurality of operating parameters of the internal combustion engine including the camshaft adjuster whose initial adjustment direction is determined in the start-up phase, wherein in this determination is not known whether the determined adjustment actually means an adjustment in the direction of the target angle to be set. In particular, probabilities can be considered in the determination of the initial adjustment direction. This implies that an initial adjustment against the adjustment direction to be selected in the adjustment phase is established with significant probability.

The transition between the startup phase, in which the adjustment direction depends on operating data at the start time, and the subsequent adjustment phase of the camshaft adjuster, in which the target angle is approached, can be triggered by two different events:

On the one hand, the start-up phase can continue until a defined position of the camshaft adjuster is reached. This may be, for example, the early position stop, the late position stop, or a clearly detectable mean position of the camshaft.

On the other hand, a transition from the start-up phase into the adjustment phase is possible as soon as the angular relationship between the camshaft and crankshaft is determined, regardless of whether a defined state of the camshaft adjuster is reached. To determine the phase relation between the camshaft and the crankshaft, angle sensors can be deflected both on the camshaft and on the crankshaft, from whose signals the phase relation between the named waves is calculated. Likewise, the camshaft adjuster, for example a highly geared transmission of the camshaft adjuster, may itself have metrological components. The measurement and control technical triggering of the adjustment phase before reaching a stop position of the camshaft adjuster takes place, if the method next to the features of claim 2 and the features of claim 1, at least for a part of the starting operations of the internal combustion engine.

Embodiments of the invention will be explained in more detail with reference to a drawing. Herein show:

Brief description of the drawings

1 and 2 each in a diagram a start strategy of a camshaft adjuster,

3 the starting strategies after the 1 and 2 in a flowchart.

Detailed description of the drawings

In 1 is the engine start phase MSP an internal combustion engine, namely a gasoline or diesel engine, illustrated, wherein the crankshaft speed n (curve K1) and the phase angle φ of the camshaft (curve K2) are shown in relation to the crankshaft in a common diagram.

The phase angle of the camshaft may be between a first stop (FN = early position of the camshaft) and a second stop (SN = late position of the camshaft). In addition, a camshaft position "fixation" (FxN) can be selected, which, however, in the embodiment of 1 not taken. Rather, the phase angle φ of the camshaft is before the start of the internal combustion engine in an undefined manner between FxN ("fixation") and FN ("early"). The positions FN, SN and Fxn are in 1 designated as camshaft positions NP.

The time when the boot process starts is in 1 denoted by T ₀ . At a time designated T ₁ , which follows shortly to T ₀ , the starter of the internal combustion engine starts to rotate its crankshaft. The time T ₀ is triggered, for example, by a manual operation of a starter button or automatically by a start-stop system. Notwithstanding this, the time T ₀ , at which the adjustment of the camshaft adjuster begins, may also be after the beginning of the rotation of the crankshaft.

With the time T ₀ , the adjustment of the camshaft begins with a first constant adjustment speed, which may be below the maximum possible adjustment speed. This adjustment is continued according to a first method variant, until the time T _2, the actual angular relation between the camshaft and crankshaft is determined by measurement and computational technology. The start-up phase of the camshaft adjuster is thus completed. This is immediately followed by the adjustment phase, in which the target value ZP of the phase angle φ of the camshaft is approached.

According to a second variant of the method, which is also in 1 is sketched, the startup phase of the camshaft adjuster continues until the time T ₃ an extreme position, in the present case FN ("early"), is reached. At the latest after a reaction time, at time T ₄ , the target value ZP of the phase angle φ of the camshaft is in turn approached, in accordance with the first method variant. In the subsequent course of the engine start phase, the phase angle φ remains as shown in the idealized illustration 1 shows, unchanged.

The diagram after 2 serves the further explanation of the start-up phase of the camshaft adjuster and is valid for both variants of the method. At time T ₀ , it is first determined in which direction the camshaft is to be adjusted, as in 2 is symbolized by a solid arrow (adjustment to "late") and a dashed arrow (adjustment to "early"). The initial adjustment direction of the camshaft depends on different boundary conditions. This means, for example, that even with the same geometric data of the internal combustion engine including camshaft adjuster, especially at identical crankshaft position and camshaft position, in a first case, namely at low oil temperature, a first adjustment is set, while under other operating conditions, with higher oil temperature in the lubricating oil circuit of Internal combustion engine, the opposite adjustment is set.

Corresponds to the adjustment direction in the embodiment 2 the indicated by the dashed arrow direction, the start-up phase of the camshaft adjuster goes as soon as possible in the adjustment phase. Otherwise, as in 2 indicated by the solid arrow, an overshoot is first overcome to adjust the camshaft to its final phase angle φ (in 2 not shown). However, such an overshoot may be useful depending on the environmental conditions, for example, to support the function of the starter. In a manner not shown, the in 2 indicated initial adjustment of the camshaft against the later adjustment either end when the position SN ("late") is reached, or - at an earlier time - already in clear measurement and computational determination of the phase angle φ of the camshaft.

The two on the basis of 1 and 2 explained variants of the method for starting a camshaft adjuster are used simultaneously in a single internal combustion engine, as the flowchart according to 3 shows.

The designated as step S1 start of the method for operating a camshaft adjuster sees the detection of boundary conditions such as target angle of the camshaft, oil temperature, cooling water temperature, outside temperature, Kurbelwellenabstellposition, crankshaft position, temperature of the electric motor of the camshaft adjuster, and temperature of a controller, also referred to as a control unit, the camshaft adjuster , in front.

On the basis of these data, it is determined in an initial routine designated S2, with which actuating speed and direction of adjustment the camshaft adjuster is operated in the start-up phase. Among other things, the dependence of the starter speed of the oil temperature is taken into account. Depending on the starter speed, it may be advantageous to adjust either "early" or "late". On the camshaft or a non-rotatably connected to the camshaft part are trigger marks, which are detected during the adjustment process. An adjustment in the direction of the end stop FN, that is to say after "early", generally means an earlier detection of the trigger marks, since these correspond to an associated camshaft sensor. In contrast, an adjustment in the direction of the end stop SN, that is, after "late", leads to a faster reaching this end stop SN and thus to a precisely known reference position.

In order to determine the initial adjustment direction in method step S2, further boundary conditions are therefore taken into account. In particular, this is the state of charge of the traction battery of the vehicle driven by the internal combustion engine. The weaker the battery is, the higher the probability that the camshaft will be adjusted in the direction of "late", since less power is required for the camshaft adjuster in this adjustment direction. A temporary fixing of the phase angle φ of the camshaft may be provided in this case. Correspondingly, an adjustment to "late" or a temporary suspension of the adjustment can be provided if the electric motor of the camshaft adjuster or the control unit that drives it has a high temperature and must be protected as far as possible before the introduction of further energy. Finally, the shape of a Nockenwellentriggerrads influence on the initial adjustment of the camshaft adjuster have.

In the next method step S3, a query is made as to whether useful information about the phase angle φ of the camshaft is already available from the angle measurement at the crankshaft and the angle measurement at the camshaft. If this is the case, the target angle ZP of the camshaft is approached in method step S4, which is referred to as the adjustment phase, which is achieved in method step S5.

As long as there is no information about the phase angle φ of the camshaft in method step S3, it is checked in method step S6 whether the camshaft has reached a known position, in particular one of the stop positions FN and SN. If this is not the case, the start-up phase is continued with unchanged adjustment direction and speed. If, furthermore, no phase angle of the camshaft is detected by sensors and computationally (S3), then the adjustment is continued until a known position of the camshaft is reached. In this case, in step S7, the transition to the target angle ZP of the camshaft according to the first method variant follows the method step S6. With the reaching of the target angle ZP in step S5, the process is also completed in this case.

reference numeral

• FN

  Early position of the camshaft

  FXN

  Fixation position of the camshaft

  K1

  Curve 1 (crankshaft speed)

  K2

  Curve 2 (phase angle of the camshaft)

  MSP

  Engine start-up phase

  n

  rotation speed

  NP

  camshaft position

  S1 ... S7

  steps

  SN

  Late position of the camshaft

  t

  Time

  T ₀ , T ₁ , T ₂ , T ₃ , T ₄

  timings

  ZP

  Target value of the phase angle

  φ

  phase angle

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102008039008 A1 [0002, 0002]
• WO 2004/027223 A1 [0003]

Claims (5)

Method for operating a camshaft adjuster of an internal combustion engine, wherein in a startup phase of the camshaft adjuster an adjustment of the camshaft takes place in a first, preliminary adjustment direction which differs from a second adjustment direction in a subsequent to the start-up adjustment phase, wherein the adjustment phase by detecting an angular relationship between the camshaft and crankshaft of the internal combustion engine is triggered before reaching an end stop (FN, SN) of the camshaft adjuster. Method for operating a camshaft adjuster of an internal combustion engine, wherein in a start-up phase of the camshaft adjuster an adjustment of the camshaft takes place with an adjustment, which is dependent on at the time (T ₀ ) of starting operating data of the internal combustion engine including the camshaft adjuster, and wherein in one of the start-up phase subsequent adjustment phase, a target value (ZP) of the phase angle φ of the camshaft is set. A method according to claim 2, characterized in that the operating data at least one of the boundary conditions air pressure, operating temperature of the internal combustion engine, crankshaft position of the engine, camshaft position of the internal combustion engine, temperature of an electric motor of the camshaft adjuster, electrical voltage provided for powering the camshaft adjuster battery, and temperature of the camshaft adjuster driving controller includes. A method according to claim 2, characterized in that in the start-up phase, the camshaft with a speed which is less than the maximum displacement of the camshaft adjuster is adjusted. Control device, which is set up to operate a camshaft adjuster according to claim 1 or 2.

Images